1. Field of Invention
This invention relates specifically to a retaining device for drill steels used on percussive rock drills.
2. Description of Prior Art
Every percussive rock drill includes certain basic features. A striking piston imparts impact energy to a drill steel and bit, a rotation mechanism causes the drill steel to rotate to give the bit a fresh rock surface to strike with each blow, and a drill steel retention mechanism allows removal of the drill steel and bit when the hole is completed.
Manufacturers of small drilling rigs, designed to drill holes in the range of 1¼ to 2 inch diameter, typically use hand-held drills that are modified for mounted use. Modifications may be as simple as removing handles and locking control valves in the “on” position. Hand-held drills have a variety of drill steel retainer designs, each with its own disadvantages. One type is too weak to resist the pulling force of a mounted arrangement. A second type can withstand a strong pulling force but sometimes cannot be opened if the drill steel becomes stuck in the drilled hole. A third type can withstand a strong pulling force but is difficult to open and expensive to manufacture.